In the chemical industry there is a great need for low-cost functionalized molecules that can be used for the production of polymers with improved performance characteristics. Polyesters comprise monomers with at least two chemical groups capable of binding together and forming a polymer chain. Molecules containing more than two functional groups can be desirable to use in polyester synthesis since they often lead to modified performance characteristics. Often such molecules are made via a complex chemical synthesis and require multiple processing steps, making them expensive and difficult to obtain. It is therefore relevant to find simple, low-cost ways of producing such molecules. In recent years, much attention has been directed towards developing efficient methods for obtaining chemical building blocks from renewable bio-based sources. Such molecules which can be produced directly from biomass at low cost, and which have the potential to be used for the synthesis of other chemicals, may be referred to as ‘platform molecules’.
One platform molecule which is available from renewable sources, is methyl vinyl glycolate (methyl 2-hydroxybut-3-enoate, MVG). It is available e.g. by zeolite catalyzed degradation of mono- and/or disaccharides, such as described in EP 2 184 270. MVG has the potential to become an important renewable platform molecule for commercially relevant applications. MVG is a small molecule with a simple structure, and yet it possesses several functional groups, providing it with ample handles for many different chemical transformations.
Recently the formation of a vinyl glycolide dimer from 2-hydroxybut-3-enoic acid has been achieved in up to 24% yield, employing a shape selective zeolite catalyst (M. Dusselier, P. Van Wouwe, A. Dewaele, P. A. Jacobs, B. F. Sels, Science 2015, 349, 78-80).
MVG has also been copolymerized with lactic acid (LA), thus providing the possibility of tuning the properties of poly-lactic acid (PLA)-based polymers. This can be done either by varying the ratio between MVG and LA or through functionalization of the reactive vinyl side chain of the MVG units (M. Dusselier, P. Van Wouwe, S. De Smet, R. De Clercq, L. Verbelen, P. Van Puyvelde, F. E. Du Prez, B. F. Sels, ACS Catal. 2013, 3, 1786-1800).
Grubbs catalysts immobilized on silica supports have been tested on various substrates for catalytic activity and product selectivity. In Table 6, entry 8, butyl vinyl glycolate was converted in nonane as solvent in the presence of 2nd generation Hoveyda-Grubbs catalyst into an adipate-type compound. However, the yield is very low, and the end product does not crystallize.
There is still a need for highly functionalized platform molecules which can be produced from renewable sources and by simple methods.